Apparatus for storing and dispensing liquefied gases



March l14, 195o o A HANSEN 2,500,249

APFARATUS FO S.TORING AND DISPENSING LIQUEFIED GASES Filed Oct. 2, 1946 2 Sheets-Sheet 1 ATTORNEY MMA AA, i195@ A HANSEN www APPARATUS Fok STORING AND DISPENSING LIQUEFIED GASES Filed out. 2, 194e y2 sheets-sheet 2 JMMW' :AWG Fi N EY Patented Mar. 14, 1950 APPARATUS FOR STORIN G AND DISPENSING LIQUEFIED GASES Odd A. Hansen, Kenmore, N. Y., assignor to The Linde Air Products Company, a corporation of Ohio Application October 2, 1946, Serial No. 700,744

(Cl. (i2-1) 13 Claims.

This invention relates to a method of and apparatus for storing and dispensing liqueiied gases which have boiling points at atmospheric pressure below 230 K.; particularly to a system for providing oxygen or nitrogen at a substantially constant superatmospheric pressure for industrial use, generated from the respective liquefied gases which are shipped to the place of consumption and supplied to the system in the liquid state.

The supply of large quantities of oxygen to industrial consumers has been effected by systems employing apparatus similar to that' of U. S. Patent No. 1,943,047. In such apparatus liquid oxygen is stored in a pressure-resistant vessel that is insulated to reduce absorption of heat from the atmosphere. Since the demands for gas are irregular and usually intermittent with periods of shut-down that may be of considerable duration, it was necessary to provide for the elects of constant heat leak to the stored liquid. Also, in such systems any withdrawal of liquid to be gasified also acts to add heat to the liquid holding vessel, thus it was necessary not only to construct the apparatus for pressures considerably in excess of the desired delivery pressure, but also to provide heavy Walled gas storage receivers and one or more pressure-reducing devices in addition to the devices for controlling the gasification of liquid oxygen to supply gaseous oxygen as required for consumption.

A principal object of the present invention is to provide a system for storing and dispensing liqueed gases and a mode of operation and control thereof that avoids the objections of systems heretofore used as indicated in part above.

Other objects of the invention are to provide a system that is fully automatic in operation; that does not require the use of gaseous storage receivers to avoid loss of gas; that permits the use of a storage Vessel constructed to withstand only a moderately higher pressure than the gas supply pressure; that supplies substantially all of the gas delivered to the consumer from direct evaporation of liqueed gas without addition of heat to the stored liquid; that supplies gas at such a constant pressure that a gas pressurereducing device is not needed; that permits recharging of the liquid container Without interruption of delivery of gas to consuming devices, thus avoiding the use of duplicate containers or a reserve storage means; and that provides for both a normal demand for gas and for suddenly imposed relatively large demands for gas for short periods with a heat energy source having 55 2 a maximum heating rate only slightly greater than that required for the normal or average demands for gas.

These and other objects of the invention will be evident from the following description taken with the accompanying drawings, in which:

Fig. 1 is a diagrammatic view illustrating a preferred embodiment of a system for the storage and dispensing of a liquefied gas according to the invention; and

Fig. 2 is a View of a schematic diagram of electrical connections for automatic control of the valves of the apparatus illustrated in Fig. 1.

This application is a continuation-impart of my copending application, Serial No. 491,746, led June 19, 1943, and which has become Patent No. 2,479,070 of August 16, 1949. n

Referring particularly to Fig. 1, there is depicted a system for storing and dispensing gaseous material such as liquid oxygen, illustrative of the principles of the invention. A supply of liquid oxygenV is held within an inner vessel I0, the walls thereof having suicient thickness and strength to withstand a pressure which need be only moderately higher than the pressure of gaseous oxygen to be delivered to the consuming devices. An outer shell Il gas-tightly surrounds the inner vessel I0, and provides an insulating space l2 which may preferably have a low apparent density filling of nely divided solid material such as magnesium carbonate and in addition, preferably is evacuated of gases to provide a powder-in-vacuum insulating means resistant to heat transfer to an exceptionally high degree. When straight powder insulation is used the insulation thickness required must be very great, such that the volume of insulation exceeds the volume of the vessel by more than With powder-in-vacuum the thickness should be less, but not less than 1A foot, the space being also evacuated to a combined gas and vapor pressure therein below 10 millimeters of mercury absolute, but not necessarily lower than 10 microns of mercury. The thickness of the insulation space and the pressure therein should be correlated within the ranges indicated and with the character of the filling to restrict heat inow therethrough to the vessel to less than 5 B. t. u. per hour per square foot of surface of the inner Vessel under a temperature differential of 200 C. as will obtain when the vessel is charged with liquid oxygen. Alternatively, straight vacuum with high polished interior surfaces could also be used for insulating the liquid provided an extremely high vacuum is maintained, however,

for vessels over two feet in diameter the powderin-vacuum insulation is usually preferable.

With a powder-in-vacuum type of insulation the pressure increase in container I during idle periods is very slow, and accordingly, the vessel may be designed for a lower maximum pressure and of lighter weight. When highly eilective powder-in-vacuum insulation is employed, the outer shell II is made gas-tight and there ls preferably provided a means for maintaining the vacuum high in order that the rate of heat leak into the liquid from the surrounding atmosphere may be kept very low so that the pressure rise in the vessel I9 is slow during periods of complete shut-down even though no gas receivers are provided in communication with the gas phase of the vessel I0, as was formerly customary. Suitable means for maintaining the vacuum may be provided in the form of a vacuum pump V, the inlet of which is connected to the interior of the shell il by the connection I4 controlled by a valve I5. The vacuum pump V may be driven by a directly connected electric motor I6.

The vessel I 0 is preferably supported independently of the filling in space I2 by suitable supports extending through the insulating space, as for example by suspending it on thin rods I3 secured at their lower ends to the vessel and at their upper ends to the wall of the shell II. The container is provided with gas and liquid conduits which pass from the inner vessel through the insulating space l2 to points outside of the shell II. The places where such conduits pass through the shell are, of course, sealed gas-tightly. One such connection l1 extends from the bottom of the inner vessel I9 to the high pressure chamber of a liquid level indicating gauge I8. The low pressure side of the gauge i8 is in pressure communication with the upper part of the inner vessel I0 through a connection i9. The connection I9 also has branches 20 and 2I connected respectively to the pressure responsive elements in pressure switches 22 and 23, the function of which will be hereinafter explained.

One connection normally employable for gas phase withdrawal, is a conduit 24 connected with the top of the inner vessel I0 to which may be connected a safety release valve 25. Preferably, there are two independent connections for withdrawal of liquid from the vessel Ill. One of these, in the form of an eduction tube 26, is the main outlet for liquid, and this passes from a point near the bottom of the vessel I0 upwardly through the upperwalls of the vessel I0 and shell Il. The eduction tube conduit 26 connects directly to the inlet end of a vaporizer passage or coil 21 disposed within a heater jacket 28. interposed in the conduit 2B is a flow-controlling valve 29 which is automatically operable by a solenoid 33. From the discharge end of the vaporizing coil 2l, the oxygen vapor passes through a conduit 3i to a superheater passage or coil 32 within a heating jacket 33. From the superheater coil 32 the warmed oxygen vapors are conducted directly to the customers pipeline or consumers apparatus by a service connection 34.

The other liquid outlet is a conduit 35 connected to the bottom of the inner vessel l0 and which forms part of a means for building and maintaining a pressure in the container I0 at a substantially constant value suitable for effecting delivery of the liquefied gas to the vaporizer 2l and superheater 32 for delivery to the service connection 34 at the desired substantially con- '4l stant pressure. Such means includes an external duid circuit beginning with the conduit 35, which connects to the inlet end of a vaporizer passage or coil 36 that is preferably surrounded by a heating jacket 31. A normally open stopvalve 35' preferably controls the conduit 35. The discharge end of the coil 36 is connected with the gas phase conduit 24 by a conduit 38. The

conduit 38 is controlled by an automatically operable valve 39 which may be operated by a solenoid 40. The conduit 38 also has interposed between the valve 39 and the conduit 24 a stopvalve 38. The vaporizer coil 36 is located below the level of the liquid in the vessel I0, and preferably somewhat lower than the lowest point on the bottom of the vessel I0. The specific construction thereof and the manner of applying heat to the gas material within the vaporizer 36 may vary depending upon circumstances. Preferably, however, the heat is supplied by a liquid heating medium passed through the jacket 31 as will hereinafter be described. The pressure building valve 39 may be located in either the gas or liquid line portions of the pressure building circuit but is more conveniently located in the gas line 38. The valve 39 is made responsive to the pressure in the vessel I0 by an electric circuit hereinafter described so that when the pressure within the inner vessel I0 falls below an operating value not much different from the service pressure desired to Ibe maintained in the conduit 34, the pressure switch 22 acts to ene'rgize the solenoid 4I) to open the valve 39 which allows liquid to flow by gravity into the vaporizer coil 36. The vapor produced passes through co'nduits 38 and 24 into the gas space of the vessel II! for building a non-equilibrium pressure therein. As soon as the pressure, exceeds a slightly higher desired operating value, the pressure switch 22 opens to deenergize the solenoid 40 which allows the valve 39 to close.

The supporting means I3 and the conduits I1, I9, 24, and 35 where they pass through the insulation space, are constructed as to material and length to provide substantial' resistance to heat conduction therethrough toward the inner vessel.

If the pressure in the inner vessel I9 should exceed the operating value, gas is allowed to pass out through conduit 24 which has its outer end connected to the conduit 3 I, so that such gas may be warmed in the superheater 32 before it is passed to the service connection 34. The portion of conduit 24 nearest the conduit 3l has interposed therein a check valve 43 opening in the direction toward conduit 3l. This portion of conduit 24 is also controlled by a control valve 4I which is operable by a solenoid 42. Also in conduit 24 between control valve 4! and the conduit 38 is a stop valve 24'. Control valve 4I is operable bythe action of the pressure switch 23, which, when the pressure in vessel I9 exceeds the operating value to be maintained, closes its circuit and energizes the solenoid 42, which opens the valve 4I. The energizing of solenoid 42 by pressure switch 23 is arranged to simultaneously deenergize the solenoid 39 so that the valve 29 will close. Thus when the valve 4I is open, valve 29 is closed and vice versa, so that liquid and gas withdrawal cannot occur simultaneously to the delivery conduit 34, and the pressure within the inner vessel il) is quickly reduced to the desired operating pressure. AIn pressure communication with the service connection 34 is a pressure switch 4t responsive to a pressure higher than the desired service pressure and arranged to be open only when such higher pressure is exceeded. Normally, pressure switch 44 is closed to permit pressure switch 23 to control valves 29 and 4I The service connection 34 also has interposed therein a temperature-sensitive element of a. thermally operable switch 45 which functions to stop operation in the event that the temperature of the outflowing oxygen falls below a predetermined minimum, for example about 40 F. Y

Means for recharging the liquid vessel l is also provided and to avoid the use of additional conduits through the insulation space l2 that might increase the paths of heat leak, use is made of the conduits 24 and 35 for lling into the gas or liquid spaces of the vessel l0. To this end there is provided a filling connection 48 having branches 41 and 48 controlled by normally closed valves 41' and 48', respectively. The branch 41 connects with the liquid phase conduit 35 at a point between valve 35' and the vaporizer coil 36. Branch 48 joins the conduit 24 between the stop valve 24 and the control valve 4I. Valves 24' and 3,5 normally remain open. Since liquid oxygen is ordinarilytransported at or near atmospheric pressure and the vessel l0 operates at a substantially constant superatmospheric pressure, the charge of liquid must be forced in against the pressure. This is conveniently done by a pumping means and a metering device which are associated with the liquid oxygen transport that would be coupled to the connection 46. The liquid oxygen delivered is of lower temperature than the contents of the vessel l0, therefore by adjusting valves 41 and 48', the delivery is proportioned between the gas and liquid phases of the vessel Il), so that the pressure in the vessel l0 may remain substantially constant. Entry of the colder liquid oxygen through the conduit 24 into the gas space tends to effect condensation of gas in the gas space so that the pressure tends to fall even though the vessel is being filled with liquid. Entry of liquid through the conduit 35 tends merely to compress the gas in the gas space at a rate faster than it can condense at the liquid surface, and thus the pressure would tend to rise unless of course the flow from the service connection 34 were great enough to prevent such rise.

The heating jackets 31, 28, and 33 are preferably heated by a liquid heating medium which is circulated with sucient rapidity to avoid any freezing thereof on the vaporizer coil. The heating liquid may be a water or a water solution, and preferably ows in a closed circuit which includes a storage tank 50 of substantial size 'to lprovide a reservoir of heat. From the bottom of the tank 50 a conduit 5l controlled by valve 5l' conducts liquid to the inlet of a water circulating pump 52 which is driven by an electric motor 53. From the pump 52 the heated water is conducted by a conduit 54 to the vaporizer heating jacket 31. From jacket 31 a connection 55 passes the water to a jacket 28 from whence it ows through a connection 56 to the heating jacket 33. From heating jacket 33 the cooled liquid is passed through conduit 51 to a heating chamber 58 located within the tank 59. The heating chamber 58 preferably empties into the upper part of the tank 50 through a tube 59. Extending into the heating chamber 58 and immersed in the liquid therein are electric heating elements indicated generally at 60. Preferably there are three sets of elements shown diagrammatically at 69a, 5017, and 60e. The tank 59 is preferably surrounded by insulating jacket 6I to avoid excessive loss of heat to the atmos- 8 phere and also has an opening in its top covered by a suitable cap 63 provided with vents 84. A valve 65 may be provided for draining the heating chamber 58 and connected to the lower end of conduit 51. A valve 66 is connected to the conduit 5I for draining the tank 50.

The tank 50 is also provided with a trycock 81 at the desired normal level of the water in the tank. A oat actuated switch 68 is preferably connected to be responsive to the liquid level in chamber 58 by tubes connecting its oat chamber with the air space in the upper part of the tank and with the chamber 58. The liquid level switch 68 functions to prevent operation of the heating elements and oxygen delivery in the event that the liquid level in chamber 58 should fall too low. Because of the heat storage provided by the mass of water in the tank 58, the electric heating elements 60 need be suiricient in size only to provide heat for vaporizing the average amount of oxygen delivered to the service conduit 34 during the day, but the volume of water is large enough so that when it is heated to a constant operating temperature, for example ol' about 123 F., a suicient reserve of heat is provided to maintain an oxygen delivery rate of about four times the average for a period of at j least one hour. The heating elements 60 are controlled by thermo switches which have their sensitive elements immersed in the water. Preferably, there are three such thermo switches 10, 1|, and 12, mounted on the conduit 54, after the pump 52, respectively controlling the three heatingr elements 60a, 60h, and 60o.

The electric circuit for effecting automatic control of the valves in the system is diagrammatically shown in Fig. 2. This circuit has been simplied by omitting protective devices such as fuses, and also by employing a two-wire current supply. The same principles are involved obviously if the system were arranged for a threephase power supply, for example. A main switch connects the power supply 8| to. lines 82 and the primary of a transformer 83, the secondary of which is connected by a two-pole switch 84 to a main control line L and aline L2. The motor i6 that drives the vacuum pump V is connected in series by a line 85 with a manual on-and-olf switch 86 across the lines L and L2. Line 85 also has interposed therein a thermal overload release switch 81. Switch 86 is closed only when it is necessary to operate the vacuum pump for improving the vacuum in the insulation l2,`

The water circulating pump motor 53 and operation of the heating elements 60 are controlled by push button switches 88 and 89 which are connected in series with a relay coil 99 by a line 9| across lines L and L2. Push button 89 is normally biased closed and is used for stopping operation and push button 88 is normally biased to open position. When push button 88 is momentarily closed, the relay coil 90 is energized and this closes a switch 92 which is shunted across the contacts of switch 88, thus when switch 88 is released the circuit for the coil 90 is maintained closed and coil 98 also holds closed a switch 93 that connects line L2 to a line L3. A relay coil 94 is connected between lines L and L3 by a line 95 and is thus energized by the closing of switch 93. Relay coil 94 closes a switch 96 which connects the motor 53 across the lines 82, thus starting the water pump 52 to operate. The liquid level switch 68 is normally closed when the correct height of liquid exists in the chamber 58 and maintains connection between line L3 and a line L4. The thermo switches 10, 1|, and 12 are connected by lines 91, 98,' and 99, respectively, in series with three relay coils |00, and |02 between line L and L4. The coils |00, |0|, and |02 respectively close switches |03, |04, and |05, which, in turn connect the heating elements 30a, 60h, and 60o across the'lines 02. The use of three temperature controls, provides greater flexibility of control. Thus, if the water temperature is less than, for example, 120 F. the temperature switch 10 will close for energizing coil |00 which closes switches |03 to energize the heating ele ment 60a. A pilot lamp PI connected across the Y coil |00 will indicate operation of the heater element. If the temperature of the water falls to a lower value, such as 11.5 F., the thermoswitch 1| will close, energizing coil |0| which closes switch |04 to put heater element 60h into operation. If the water temperature should fall still lower to, for example, 110 F., thermo-switch 12 will close for energizing coil |02, closing switch |05, and putting heating element 60e into operation. As the temperature of the water rises, the temperature switches will be opened in the reverse order to cut off the heaters which they control vand extinguishing the respective pilot lights shunted across the coils.

Operation of oxygen delivery is initiated by momentarily' closing a push button switch |01. Normally open switch |01 is connected in series with a normally closed switch |08 usable to stop operation, a relay coil |09, and the contacts of the thermo-switch 45 which is also normally closed, all connected by line ||0 between line L and line L4. Coil |09 closes switches and H2, being shunted across push-button |01 so that the coil |09 will remain energized. Switch H2 connects line L4 with a line L5. A line ||3 connected between L and L5 connects the pressure switch 22 in series with the: coil of solenoid 40 which operates Valve 39. A normally closed manually operated switch IM is also interposed in the line ||3, in order when desired to connect solenoid 40 into or to isolate it from the control circuit. The pressure switch 44 is connected between line L5 and a line L6. Pressure switch 44v is normally closed and opens only when the pressure in service conduit 34 exceeds the desired service pressure by a. predetermined amount. Pressure switch 23 controls two sets of contacts, an upper set ||5 which are normally disconnected and are connected only when the pressure in the vessel |0 exceeds the desired working value and a lower set IIS. Contacts I6 are always closed unless the pressure in the vessel exceeds the operating value by a small amount when the contacts ||5 will be closed. Contacts ||5 are connected in series with the coil 42 controlling valve 4| by a line ||1 between line L and L6. Similarly, contacts ||6 are connected in series with the coil 30 which controls valve 29 by a line ||8 between lines L and L6. In order to manually select withdrawal of liquid alone, or to permit liquid withdrawal through line 48 in an emergency, manual on and off switches 9 and |20 are interposed in lines ||1 and ||8, respectively, and manually operated on-and-off switches |2| and |22 are shunted across the contacts ||5 and H0, respectively. If desired, indicator or pilot lights P4, P5, and P6 may be shunted around the coils 40, 42, and 30, respectively, to indicate operation of the valves 39, 4|, and 29.`

As previously indicated, the system is prepared for operation by closing switches 30 and connected between line Land Ld will indicateA` whether switch 38 is closed and whether operation of the oxygen delivery circuit can be started. Push button |01 is then momentarily closed to initiate oxygen delivery, and operation from then on is automatic unless push button switch |03 is opened, or the thermo-switch 45 should open due to too low a temperature of the oxygen leaving the system through service conduit 30. Pressure switch 22 is then in control of the solenoid 40 of automatic valve 39 to keep the pressure within the vessel i0 at a predetermined substantially constant operating pressure which is only slightly higher than the service pressure desired in the service conduit 34. If such pressure tends to exceed the predetermined value, valve 39 remains closed; but if the operating pressure tends to drop below the predetermined value, the switch 22 closes and opens valve 39 allowing liquid to iiow into the pressure building vaporizer 30, which then delivers gas through the line 24 into the vessel i0. The valves 38', 24', and 35 are open during normal operation. This pressure building control can be made so sensitive that it is not necessary to provide pressure-reducing regulators in the service conduit 34, as was formerly necessary.

hUnder normal operating conditions the pressure switch 44 remains closed and when the consumption of gas from service conduit 30 tends to reduce' the pressure therein, the small differ'- ence in pressure, for example, about l p. s. i, between vessel |0 and service conduit 34 causes flow of liquid through the eduction tube 26 into the vaporizer 21 and superheater coil 32, which path provides the main source of oxygen for the service conduit 34. Normally valve 29 is open due to energization of solenoid 30 by the closed .lower contacts IIE of switch 23. When the pressure in service conduit 34 tends to exceed the desired service pressure, the differential pressure causing flow is reduced resulting in less liquid vaporization. If, for example, after a shut-down period the pressure in vessel l0 should be at a higher value than the predetermined operating pressure, the pressure switch 23 will open the contacts I IE, and close the contacts H5. In that event, if the service line pressure is reduced by consumption to keep the pressure switch 44 closed, the circuit through the solenoid 30 will be opened and the circuit to the solenoid 42 will be energized so that the valve 4i will open, and the gas will iiow from the upper part of the vessel |0 through the conduit 24, conduit 3|, and superheater 32 to the service conduit 34.' Gas withdrawal through such gas phase passage will continue until the pressure in vessel I0 has reduced to the operating value when valve 4| will be closed by the opening of contacts ||5 and valve 29 will be opened.

In some instances the gas to-be supplied to the consuming apparatus will be a. mixture rather than a single pure gas. Thus commercial oxygen is not 100% oxygen but contains 99.6% oxygen, the balance being mainly nitrogen with some argon. Ordinarily a slight change of purity in this range is of no consequence but often it is desired to deliver a mixture of gases such as a mixture of oxygen and nitrogen of constant composition. This may be accomplished with the system described herein because it is possible to operate substantially solely with liquid phase withdrawal. Due to the diiierence of boiling points of gases in a mixture of gases, the composition of the gas phase or vapor in the gas space when in equilibrium with a liqueiied gas mixture in the vessel I0, will differ substantially from the composition of the liquid phase; thus by complete gasication of liquid drawn from the liquid phase only, the composition of the stored liquid will remain constant and the gas mixture delivered to the service connection 34 will remain of constant composition.

Operation with liquid phase withdrawal alone is obtained by opening switch I|9 and closing switch |22, making valve 29 solely responsive to pressure switch 44. Because of the high efliciency insulation of the vessel I0, and because no heat is added to the contents of the vessel l by the system employed for vaporizing the withdrawn liquid to produce gas for the service connection, and unless a period of complete shutdown should be of abnormally long duration, there will usually be no excessive pressure rise in the vessel I0. If, due to an abnormally long shut-down, the pressure should increase to a value for which the relief valve 25 is set, some gas will be blown ofi' but the amount will be small because the rate of heat leak is very slow.

During a shut-down the heat leak to the vessel ill from the atmosphere is absorbed mainly as sensible heat in the liquid and vessel and with a vessel of substantial size a long period would elapse before the pressure in the vessel reaches a predetermined value above the operating service pressure.

The effectiveness of powder-in-vacuum insulation for the liquid holding vessel in the system of the present invention is shown by the following measurements of typical installations of the pressure rise during a complete shut-down. With an installation substantially according to the disclosure of U. S. Patent No. 1.943.047 and in which the insulation was a 1 foot thickness of magnesium carbonate powder, at atmospheric pressure the pressure rise when the vessel was full was 3 p. s. i. per hour and 72 p. s. i. per day, and when 1A; full the pressure rise was 10 p. s. i. per hour and 240 p. s. i. per day. With an installation according to the present invention, the pressure rise with vessel i0 iilled was .09 p. s. i. per hour and only 2.2 p. s. i. per day, and when 1A full the pressure rise was .36 p. s. i. per hour and only 9 p. s. i. per day.

It is seen that even after several days complete shut-down the pressure rise is moderate. rIhus, for example, the container l0 can be constructed for a pressure of say only 50 p. s. i. above the service pressure and when only 1A full there could be over iive days complete shut-down before blow-off pressure is reached. If the shutdowns are normally of only two days duration, operation may be with only liquid phase withdrawal without any loss of gas.

If desired the eduction tube 26 could be omitted and the inlet to the valve 29 could be connected to the line 35 or line 4l and thus eliminate a conduit through the insulation space l2, If repairs are to be made to valve 29, it can be isolated by closing suitable stop valves in conduit 26 not shown, and operation continued by sealing charging connection 4B, opening valves 41 and 48' and closing valve 24'. Liquid then iiows through conduits 35, 41, 48, valves 4|, 43, conduit 3|, and heater 32 to the service connection 34. Pressure switch 44 is then placed in sole control of valve 4| by closing switch I 2| and opening switch |20.

What is claimed is:

1. In a system for storing liquefied gas having a boiling point below 233 K. at atmospheric pressure and dispensing gas material therefrom, the combination of a pressure Vessel for holding a supply of the liquefied gas and having normal liquid and gas spaces therein; heat insulation surrounding said vessel of a thickness and character such that heat inflow through the insulation to said vessel is restricted to no more than about 5 B. t. u. per hour per square foot of surface of the vessel under a temperature differential of 200 C.; a service connection for consuming apparatus requiring gas material at adesired service pressure; automatic pressurizing means including an external vaporizer having connection to the gas and liquid spaces of said vessel and an automatic fluid control device intrposed therein and having an operating element arranged to respond to changes of pressure in said vessel for controlling the vaporization of portions of liqueiied gas in response to pressure in said vessel to maintain the pressure therein at a predetermined substantially constant operating value within selected limits; and withdrawal passage means connected between said vessel and said service connection for supplying gas material thereto at a substantially constant service pressure and including means connected to be responsive to demand for stopping suoli supply of gas material when the demand for gas by the consuming apparatus ceases; the heat leak to said vessel then being absorbed mainly as sensible heat in the liquid and vessel for an abnormally long period of no demand before the pressure in the vessel reaches a predetermined value above said service pressure.

2. In a system for storing liquefied gas and dispensing gas material therefrom according to claim 1, in which said withdrawal means includes a gas phase passage connection between the gas space of said vessel and said service connection, a liquid phase passage connection including a vaporizer between the liquid space of said vessel and said service connection, and automatic valve means interposed in said passages and constructed so as to control iiow therein to pass gas from the gas phase of said vessel to the service connection only when the pressure in the vessel exceeds said predetermined substantially constant value.

3. In a system for storing liquefied gas and dispensing gas material therefrom according to claim 1, in which said withdrawal means includes a gas phase passage connection between the gas space of said vessel and said service connection, a liquid phase passage connection including a vaporizer between the liquid space of said vessel and said service connection, a first automatic valve means in said gas phase connection, a second automatic valve means in said liquid phase connection, means responsive to pressure in said service connection and operatively connected to said first and second automatic valve means for allowing either of said automatic valve means il to open at all times except when the service connection pressure rises above a substantial amount higher than the desired service pressure, and means responsive to pressure in said vessel and operatively connected to said first and second automatic valve means for opening -said iirst automatic valve means only when the pressure in the vessel exceeds said predetermined substantially constant value and for allowing opening of said second automatic valve means when the pressure in said vessel does not exceed said predetermined substantially constant value.

4. Apparatus for supplying gas material in the gas phase converted from liquefied gas having an atmospheric boiling point below about 233 K. and comprising a heavy Walled pressure-resistant inner vessel for holding a body of such liquefied gas under a substantial superatmospheric pressure; a larger gas-tight shell completely encompassing said inner vessel providing therewith an intervening evacuatable insulation space having a minimum thickness of not less than 1A foot, said space containing a loW apparent density filling of finely divided solid material and being evacuated to a combined gas and vapor pressure therein below 10 millimeters of mercury absolute, the thickness of said space and the pressure therein being correlated within the specified` ranges and with the character of the lling to restrict heat iniiow through the insulation to said vessel to less than 5 B. t. u. per hour per square foot of surface of the inner vessel under a temperature differential of 200 C.; means extending through said insulating space for supporting said inner vessel in spaced relation to said shell independently of said filling; a liquid conduit communicating with the bottom of said inner vessel, and a gas conduit communicating with the upper part of said inner vessel, both said conduits passing by an elongated path through said space to the exterior of said shell, said supporting means and conduits being constructed and arranged to provide substantial resistance to heat conduction therethrough; and means for supplying gas at a desired service pressure to a service connection for consuming apparatus, including passage means connecting both the liquid conduit and the gas conduit to said service connection, liquid vaporizing means interposed between said liquid conduit and said service connection, and automatic valve means interposed in said liquid and gas conduits and having operating means responsive to the service connection pressure and the vessel pressure and constructed and arranged to selectively control the ow through said liquid conduit and said gas conduit toward said service connection and arranged to vaporize liquid at a rate required for supplying gas to the service connection at the service pressure as demanded by the consuming apparatus and preferentially to feed gas phase toward said service connection when the pressure in said vessel exceeds said service pressure, and to stop said feeding of gas and vaporization of liquid during periods of no demand for gas by the consuming apparatus, the heat leak to said body of liquefied gas being so low that it is absorbed as sensible heat in the liquid and vessel for an abnormally long period of no demand before the pressure in the vessel reaches a predetermined value above said service pressure.

5. In a system for storing liquefied gas having a boiling point below 233 K. at atmospheric pressure and dispensing gas material therefrom, the combination of a pressure vessel for holding a supply of the liqueiled gas and having normal liquid and gas spaces therein; heat insulation surrounding said vessel of a thickness and chai"- acter such that heat inilow through the insulation to said vessel is restricted to no more than about 5 B. t. u. per hour per square foot of surface of the vessel under a temperature differential of 200 C.; a service connection for consuming apparatus requiring gas material at a desired service pressure; means including. an external vaporizer having connection to the gas and liquid spaces of said vessel and an automatic fluid control device for controlling the vaporization of portions of liqueiied gas in response to pressure in said vessel to maintain the pressure therein at a predetermined substantially constant value, such pressure building means being constructed and arranged to maintain the operating pressure within a small range of said predetermined value and to shut on completeiywhen the pressure is above said range; and withdrawal means connected between said vessel and said service connection for supplying gas material thereto at a rate corresponding to the consumption demand, said withdrawal means comprising a liquid phase connection including a vaporizer between the liquid space of said vessel and said service connection, and a iiow controlling device interposed therein constructed and arranged to respond to service pressure so that a relatively small differential of pressure between said vessel and said service connection effects ilow of liquid to the vaporizer at a rate for producing gas corresponding to the demand, such flow stopping when the demand ceases, the heat leak to said vessel then being absorbed mainly as sensible heat in the liquid and vessel for an abnormally long period of no demand before the pressure in the vessel reaches a predetermined value above said service pressure.

6. In apparatus for storing liquefied gas having a boiling point below 233 K. at atmospheric pressure and dispensing gas material therefrom, Y

the combination of an insulated pressure container for liquefied gas having normal liquid and gas spaces therein.- a service connection for consumption apparatus, a gas withdrawal line connected between said container and said service connection, an external 'iiuid circuit having a connection to the bottom of said container and arranged to receive liquid therefrom under gravity and having an opposite connection to the gas space of said container, heating means in said circuit located at least in part lower than the bottom of said container, automatically controlled valve means in said circuit responsive to the pressure in said container to control ciculation through said heating means and adapted thereby to maintain the pressure in said container above a predetermined value, a liquid withdrawal -line connected to withdraw liquefied gas from said container independently of said fluid circuit and to deliver gas generated from the withdrawn liquid to said service connection, said liquid withdrawal line having interposed therein vaporizing and superheating means, and means responsive to pressure in the service connection and operative to control flow through said liquid withdrawal line for effecting preferential liquid withdrawal when the pressure in the service connection tends to fall below a desired value under that of the container.

7. In a system for storing liquefied gas having a boiling point below 233 K. at atmospheric pressure and dispensing gas material therefrom,

the combination of a pressure vessel for holding a supply of the liqueed gas and having normal liquid and gas spaces therein; heat insulation surrounding sail' vessel for restricting ilow ofv heat thereto to a low value; a service connection for consuming apparatus requiring gas material at a desired service pressure; means including an external Vaporizer having connection to the gas and liquid spaces of said vessel and an auto matic iiuid control device for controlling the vaporization of portions of liquefied gas in response to pressure in said vessel to maintain the pressure therein at a predetermined substantially constant operating value; a gas phase passage between the gas space of said vessel and said service connection; a liquid phase passage inl cluding a vaporizer between the liquid space of said vessel and said service connection; automatically operable valve means in each oi said passages; and pressure responsive means connected and arranged for operating said valve means to open the valve in the gas phase passage when the pressure in the vessel exceeds said operating value by a desired amount, and to allow only the valve in the liquid phase passage to be open when the pressure in said vessel does not exceed said operating value by said desired amount.

8. ln a system for storing iiqueed gas and dispensing gas material therefrom according to claim 'l which includes pressure responsive means normally allowing either of said automatically operable valve means to open and stopping such opening when the pressure in the service line exceeds said desired service pressure by a predetermined amount.

9. In a system for storing liqueed gas and dispensing gas material therefrom according to claim 7, a superheater interposed between said service connection and said gas phase and liquid phase passages to maintain the gas material delivered to said service connection normally at a temperature higher than about 40 F.

l0. In a system for storing liquefied gas having a boiling point below 233 K. at atmospheric pressure and dispensing gas material therefrom, including an insulated pressure vessel for holding a supply of liquefied gas having normal liquid and gas spaces therein, a service connection,

means for controllably supplying gas material to said service connection, and means including an external vaporizer and an automatic fluid control device for controllably vaporizing portions of the liqueed gas in response to pressure in said vessel to maintain the pressure therein at a predetermined substantially constant value; the combination with a heating chamber for heating said vaporizer; a heating fluid 'circuit with a heating iluid therein connected to circulate heating fluid through said chamber: and a tank for holding a substantial quantity of said heating iiuid interposed in said circuit and ballast to supply sudden large demands for heat at the vaporize n.msimianimmuni:luiueiieamimaudispensing gas material therefrom according to claim l0, heating means for said heating uid having a heat-producing power not greater than sumcient to provide heat required for an average demand by the vaporizer, the sum of the heating power of the heating means and the available stored heat of the heating fluid being sumcient to supply the maximum demand for heat for a substantial period.

Y l2. In a system for storing liquefied gas and dispensing gas material therefrom according to claim l0, in which said means for controllably supplying gas material to said service connection includes a liquid phase passage from the liquid space ci said container with a vaporizer interaposed therein, and a second heating chamber for .the last mentioned vaporizer, said second heating chamber being interposed in said heating duid circuit.

'ing a boiling point below 233 K. at atmospheric i3. ln a system for storing liqueed gas havpressure and dispensing gas material therefrom, the combination of a pressure vessel for holding a supply oi the liqueed gas and having normal liquid and gas spaces therein; heat insulation surrounding said vessel of a thickness and char service pressure; means including an external providing sulcient heat vaporizer having connection to the gas and liquid spaces of said vessel and an automatic iluid control device for controlling the vaporization of portions of liqueiied gas in response to pressure in said vessel to maintain the pressure therein at a predetermined substantially constant operating value; a withdrawal means comprising a liquid phase passage including a vaporizer between the liquid space of said vessel and said service connection; and an automatic valve in said passage responsive to the operating pressure for permitting ilow to said service connection when the pressure therein tends to fall below the desired service pressure and stopping flow when the pressure in said vessel exceeds said operating pressure.

, ODD A. HANSEN.

REFERENCES cr'rnn Umm s'raTEs PAimNTs Number Name Date 2,226,810 Ensign et al. Dec. 31, 1940 2,346,112 Melsheimer Apr. 4, 1944 2,352,775 Dittmer July 4, 1944 2,862,968 Bliss et al. Nov. 22, 1944 2,363,960 Hansen Nov. 28, 1944 2,396,459 Dana Mar. 12, 1946 2,435,332 Van Vleet et al. Feb. 3, 1946 

